Measurement of the η mass at KLOE Di Micco, B.
European physical journal. A, Hadrons and nuclei,
11/2008, Volume:
38, Issue:
2
Journal Article
Peer reviewed
Open access
In this report the measurement of the η mass is presented. The analysis has been performed on 450pb^-1 of data collected in the years 2001 and 2002. The measured value is
m
η
= (547.874±0.07
stat
...±0.029
syst
) MeV.
We have measured the overall detection efficiency of a small prototype of the KLOE PB-scintilation fiber calorimeter to neutrons with kinetic energy range 5,175 MeV. The measurement has been done in ...a dedicated test beam in the neutron beam facility of the Svedberg Laboratory, TSL Uppsala. The measurements of the neutron detection efficiency of a NE110 scintillator provided a reference calibration. At the lowest trigger threshold, the overall calorimeter efficiency ranges from 28% to 33%. This value largely exceeds the estimated ∼8% expected if the response were proporetional only to the scintillator equivalent thickness. A detailed simulation of the calorimeter and of the TSL beam line has been performed with the FLUKA Monte Carlo code. The simulated response of the detector to neutrons is presented together with the first data to Monte Carlo comparison. The results show an overall neutron efficiency of about 35%. The reasons for such an efficiency enhancement, in comparison with the typical scintillator-based neutron counters, are explained, opening the road to a novel neutron detector.
In this report the extraction of the η ,
mixing angle and of the
gluonium content from the
R
φ
=
Br
(φ(1020) →
γ)/
Br
(φ(1020) → ηγ) is updated. The
gluonium content is estimated by fitting
R
φ
, ...together, with other decay branching ratios. The extracted parameters are:
Z
2
G
= 0.12±0.04 and ϕ
P
= (40.4±0.9)
°
.
Among some 400 million KSKL pairs produced in e+e− annihilations at DAΦNE, ∼6500 each of KS→π+e−ν¯ and KS→π−e+ν decays have been observed with the KLOE detector. From these, the ratio ...Γ(KS→πeν)/Γ(KS→π+π−)=(10.19±0.13)×10−4 is obtained, improving the accuracy on BR(KS→πeν) by a factor of four and providing the most precise test of the ΔS=ΔQ rule. From the partial width Γ(KS→πeν), a value for f+K0(0)×Vus is obtained that is in agreement with unitarity of the quark-mixing matrix. The lepton charge asymmetry AS=(1.5±9.6stat±2.9syst)×10−3 is compatible with the requirements of CPT invariance. The form-factor slope agrees with recent results from semileptonic KL and K+ decays. These are the first measurements of the charge asymmetry and form-factor slope for semileptonic KS decays.
We present a measurement of the ratio R=Γ(K
0
e3γ
;E
*
γ
> 30 MeV, θ
*
γ
>20
°
)/Γ(K
0
e3
) and a first measurement of the direct emission contribution in semileptonic K
L
decays. The measurement was ...performed at the DA NE φ factory by selecting φ→K
L
K
S
decays with the KLOE detector. We use 328 pb
-1
of data, corresponding to about 3.5 million K
0
e3
events and about 9000 K
0
e3γ
radiative events. Our result is R=(924±23
stat
±16
syst
)×10
-5
for the branching ratio and 〈X〉=-2.3±1.3
stat
±1.4
syst
for the effective strength parameter describing direct emission.
We have studied the η→π+π−e+e−(γ) decay using about 1.7 fb−1 collected by the KLOE experiment at the DAΦNE ϕ-factory. This corresponds to about 72 millions η mesons produced in ϕ radiative decays. We ...have measured the branching ratio, inclusive of radiative effects, with 4% accuracy: BR(η→π+π−e+e−(γ))=(26.8±0.9Stat.±0.7Syst.)×10−5. We have obtained the first measurement of the CP-odd ππ–ee decay planes angular asymmetry, Aϕ=(−0.6±2.5Stat.±1.8Syst.)×10−2.
We present a measurement of the K–π vector current form-factor parameters for the decay KL→π±e∓ν. We use 328 pb−1 of data collected in 2001 and 2002, corresponding to ∼2 million Ke3 events. ...Measurements of semileptonic form factors provide information about the dynamics of the strong interaction and are necessary for evaluation of the phase-space integral IKe needed to measure the CKM matrix element |Vus| for KL→π±e∓ν decays. Our result is λ+=(28.6±0.5±0.4)×10−3 for a linear fit, and λ+′=(25.5±1.5±1.0)×10−3, λ+″=(1.4±0.7±0.4)×10−3 for a quadratic fit.
We have measured the fully inclusive K+→μ+ν(γ) absolute branching ratio with the KLOE experiment at DAΦNE, the Frascati ϕ-factory. From some 865 283 K+→μ+ν(γ) decays obtained from a sample of ...∼5.2×108, ϕ-meson decays, we find BR(K+→μ+νμ(γ))=0.6366±0.0009stat.±0.0015syst., corresponding to an overall fractional error of 0.27%. Using recent lattice results on the decay constants of pseudoscalar mesons one can obtain an estimate for the CKM mixing matrix element |Vus|=0.2223±0.0026.
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